<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width, initial-scale=1.0" charset="utf-8">
</head>
<body>
<form id="upload-form" enctype="multipart/form-data">
    <div>indexThree file page</div>
    <input type="file" id="upload" name="upload"/>
</form>
<script>
    function getFontSize() {
        let fontSize = window.getComputedStyle(document.body, null).getPropertyValue('font-size')
        console.log(fontSize)
        return fontSize
    }
</script>
</body>
</html>